I have a challenge... for video tracking.

Discussion in 'Mac Programming' started by ProjectManager101, Oct 12, 2015.

  1. ProjectManager101 Suspended


    Jul 12, 2015
    Ok guys...

    I need some sort of bluetooth or wifi transmitter that I can use as a tracking device.

    I want to have this girl dancing, a bailarina, and I want to have the trace of her feet draw on the floor. I have the guy who can do the projector and video mapping and all that. But he usually uses infrared or camera tracking. I was wondering if I could get a device on her ancles to track her movements, just of the ancles. And use that data to draw in real time with the projector.

    I need to know if there is such device, I do not know if an Apple Watch with gyroscope or some sort of gyroscope that can transmit the data to a computer. Once the data transmitted we can take care of the rest.

    Thank you very much.
  2. chown33 macrumors 604

    Aug 9, 2009
    You've posted in the Mac Programming forum, but it's not a programming question.

    The questions that immediately come to mind for me are:

    1. What's your budget?
    2. What's your deadline or time frame?
    3. What programming do you expect to do for it?
  3. ProjectManager101 thread starter Suspended


    Jul 12, 2015
    I have no bodged in mind, the least expensive I believe. No deadline, is a proposal. I have the programmer.

    I mean, I believe that attaching 2 iPhones to each of her ancles to send the signal by some application would do. I I wonder if there is some sort of tracker mean for that sort of thing and wireless.
  4. balamw, Oct 13, 2015
    Last edited: Oct 13, 2015

    balamw Moderator


    Staff Member

    Aug 16, 2005
    New England
    While not a programming question per se, I can't think of a better place for this in the forums.

    There are devices specifically designed for this for specific sports, e.g.


    The basketball one might be the most appropriate as it is designed for measuring rotations etc...

    Figuring out what the sensor data actually means will be the most interesting part of this project.

    EDIT: For a more DIY/programming related approach. You could build your own sensors based on Arduino compatible IMUs and get the raw data you need. See the guide here for examples:


  5. teagls, Oct 14, 2015
    Last edited: Oct 14, 2015

    teagls macrumors regular

    May 16, 2013
    I have some experience in doing in-door localization. You need ideally a sensor with accelerometer + gyroscope + compass and some type of kalman filtering to get the most accurate movement data. Then because your actor will be within a confined area you can use dead reckoning + dimensions of the stage to convert those movements to locations on the stage. The reason you need accelerometer + gyroscope + compass is because the accelerometer measures just acceleration on a fixed axis inside of the devices accelerometer chip. So the gyroscope is used to apply that acceleration in the correct orientation. As you rotate the axis of the device changes so you have to correctly account for those changes. The compass is then needed to maintain calibration on the gyroscope and establish a consistent orientation and reference point. 30 degrees of rotation means nothing if you don't have a reference point. Lastly, on the software side you need something like kalman filtering because you will get drifting from the data.

    Another option is to use video tracking. This solution depends on the setup. Lets assume the actor is on stage by him or herself and there are no other props or people present moving in and out. You can do a simple background subtraction to very easily find the actor. Create a binary image from this and do boundary analysis with blob extraction to find the position in the video and then map that to the stage.
  6. bjet767 macrumors 6502a

    Oct 2, 2010
    Could the question be this, "What is the least expensive way of tracking a dancer's movement?"

    From experience a GPS does not have the kind of accuracy you need.

    What you might do is what the movie people do:

    1. Set up the area as a"green" screen.
    2. Dress dancing in similar color.
    3. Put contrasting color spots on the dancer where you want the movement tracked.
    4. Video the dance.
    5. Analyze the recorded video by blocking out the "green" color.

    But this is probably what your "guy" may already do.

    An acceptable device which can measure the small distance changes of a dancer's body and the associated receiving equipment would probably be outside of the budget of even a modest film studio.
  7. teagls macrumors regular

    May 16, 2013
    The 2nd solution I gave is easier and more simpler then using a green screen and all that extra setup. On the hardware side you can do it with a 10 dollar webcam. On software side python, and OpenCV computer vision framework both of which are free.
  8. bjet767 macrumors 6502a

    Oct 2, 2010

    This best part about these forums is finding something like open cv. I'm looking into it myself for some simple ideas in video..

  9. teagls macrumors regular

    May 16, 2013
    Glad I could help someone out. OpenCV is a fantastic open source framework. They also offer lots of demo, tutorials, and examples. What I also like most about it is they explain the science/math of the underlying techniques for edge detection, hough transform, etc.

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8 October 12, 2015